The present application claims priority to Japanese Application No. P10 019108 filed Jan. 30, 1998 which application is incorporated herein by reference to the extent permitted by law.
The present invention relates to a display and a plasma light-emitting device used for the display, and particularly to a plasma addressed liquid crystal (PALC) display (hereinafter, referred to simply as xe2x80x9cdisplayxe2x80x9d) and a plasma light-emitting device suitably used for the display.
As the display of this type, there is known a type shown in FIG. 3. For the sake of clarity, only one pixel of the display 1 is shown in FIG. 3.
Referring to FIG. 3, the display 1 includes a plasma light-emitting unit 12. In the plasma light-emitting unit 12, a first glass substrate 4 is stacked via a first sheet polarizer 3 on a backlight 2 formed of a dispersion type AC-drive type electroluminescence (EL) element. A cathode electrode 5 and an anode electrode 6 connected to a DC power supply 7 and/or an AC power supply 8 are disposed on the first glass substrate 4 at specific positions. An insulating layer 10 made from an insulating material such as glass is fixed on the first glass substrate 4 via O-rings 9 each being made from a rubber material such as Biton. An enclosed space 11, which is formed by the first glass substrate 4, O-rings 9 and insulating layer 10, is filled with an inert gas such as argon at a specific pressure.
In this plasma light-emitting unit 12, after the backlight 2 is turned on by an external control mean (not shown), specific voltages are applied to the cathode electrode 5 and anode electrode 6 from the DC power supply 7 and/or the AC power supply 8 in such a manner that the cathode electrode 5 comes into a negative potential relative to the anode electrode 6, to produce discharge, thereby generating plasma 13 in the space 11. The generation of the plasma 13 is able to produce charged particles (not shown) in the space 11.
On the insulating layer 10 of the plasma light-emitting unit 12 are sequentially stacked a liquid crystal layer 14 made from liquid crystal of, for example, twisted nematic (TN) type; a color filter layer 15 such as RGB vertical stripe type; an electrode layer 16, for example, made from a transparent conductive oxide having an electrically low resistance (for example, SnO2 or ZnO); a second glass substrate 17; and a second sheet polarizer 18.
While not shown, potential difference generating means is connected between the electrode layer 16 and the anode electrode 6 within the plasma light-emitting unit 12 in order to generate a potential difference therebetween on the basis of the potential of the anode electrode 6.
The operation of this display 1 will be described below. A voltage, which is supplied between the electrode layer 16 and the anode electrode 6 from the potential difference generating means, is applied to the liquid crystal layer 14 and the insulating layer 10 by utilizing, as a switching element which is the charged particle produced when the plasma 13 is generated by the plasma light-emitting unit 12. At this time, by applying the voltage the liquid crystal layer 14 is charged. When the charged particles disappear after an elapse of a specific time since completion of the discharge of the plasma 13, the inside of the space 11 comes into the insulating state and thereby any voltage is no longer applied to the liquid crystal layer 14. The liquid crystal layer 14 holds the stored charges until the next discharge occurs.
In this way, the display 1 is able to display an image by performing scanning in line sequence through operation of cutting off transmission light supplied from the backlight 2 or transmitting the light by control of the liquid crystal layer 14 in combination with operation of the first and second sheet polarizers 3 and 18.
The above display 1, however, has a problem that the liquid crystal layer 14 is deteriorated by ultraviolet light (not shown) produced when the plasma 13 is generated by the plasma light-emitting unit 12. Concretely, by the effect of ultraviolet light, rust gradually permeates into the liquid crystal layer 14, to discolor the liquid crystal layer 14 into yellow, thereby degrading an image displayed on the display 1.
Another problem of the above display 1 is that the insulating layer 10 formed of a thin film is easily cracked. This makes the handling characteristic poor. To solve this problem, it may be considered to form the insulating layer 10 using a high polymer material (plastic or the like) in place of glass. In this case, however, there occurs an inconvenience that the high polymer material is deteriorated, that is, discolored into yellow by the effect of ultraviolet light produced when the plasma 13 is generated, as described above.
Further, the latter manner using a high polymer material for forming the insulating layer 10 has another disadvantage. That is to say, since the insulating layer 10 made from a high polymer material allows moisture in atmospheric air and an inert gas sealed in the space 11 to excessively pass therethrough, it is difficult to keep the vacuum state constant within the space 11. As a result, each of the cathode electrode 5 and anode electrode 6 is easily stuck with impurities (for example, moisture in atmospheric air) by sputter generated in discharge, to shorten the service life of the cathode electrode 5 and the anode electrode 6, thereby degrading the life of light emission by the plasma 13. Also since the light emission amount of the plasma 13 is changed by the impurities, variation in pressure, and so on, it is difficult to keep a stable light emission state of the plasma 13 and a stable quality of a displayed image.
A further problem of the display 1 mentioned above is that the insulating layer 10 formed of a single thin film is deflected by a stress caused by the negative pressure in the space 11.
An object of the present invention is to provide a plasma light-emitting device capable of keeping a stable light emission state of plasma and a stable quality of a displayed image, and a display using the plasma light-emitting device.
To achieve the above object, according to an aspect of the present invention, there is provided a plasma light-emitting device including: means for generating plasma; and means, provided on a specific surface of the plasma generating means, for preventing ultraviolet light, produced when the plasma is generated by the plasma generating means, from leaking outside.
Consequently, in this plasma light-emitting device, it is possible to prevent ultraviolet light produced when the plasma is generated, from leaking outside, and hence to keep a stable light emission state of plasma and a stable quality of a displayed image.
According to another aspect of the present invention, there is provided a display including: means for generating plasma; means, provided on a specific surface of the plasma generating means, for preventing ultraviolet light, produced when the plasma is generated by the plasma generating means, from leaking outside; a liquid crystal layer which is made from liquid crystal and is disposed on the ultraviolet light leakage preventive means; an electrode layer which is made from a transparent conductive oxide and is stacked on the liquid crystal layer; and means for generating a potential difference between the plasma generating means and the electrode layer.
In this display, it is possible to prevent ultraviolet light which is produced when the plasma is generated, from leaking outside, hence to keep a stable light emission state of plasma and a stable quality of a displayed image.